Drawing ASTs for expressions: Correct Solution

For each of the Java expressions below:

• Draw an AST for the expression.
• Show how the expression evaluates at each node in the tree.

Be sure that your tree accurately reflects how Java would evaluate the expression.

Part 1

Given the following variables:

int onder = 8;
int le = 2;
double ia = 3.0;
double supriod = 3.0;

...draw the AST and evaluation results for the following expression:

onder + le % 9 - 7 - 0 + ia * (supriod * 7)

Solution

Things to double-check in your solution:

• Do you have the left and right branches on the correct side?
• Did you indicate the difference between ints and floating point values?

Part 2

Given the following variables:

boolean sedri = true;
int staclen = 5;
int pesba = 2;
int istwin = 9;
int assti = 4;
int verbe = 9;
int an = 2;
int chisskor = 1;

...draw the AST and evaluation results for the following expression:

sedri || staclen == 0 || (3 >= pesba != !(istwin >= assti) == 2 < 7) == (3 == verbe) == an > chisskor

Solution

Things to double-check in your solution:

• Does your tree correctly reflect the precedence of && and ||?
• Did you correctly show short-circuiting? (That is when the right branch of && or || is never evaluated because the left branch already determines the answer.)

Part 3

Draw the AST and evaluation results for the following expression:

0 + 1 + 2 + 3 + 4 + 5 + 6 + "7" + 8

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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